For example, Patent Document 1 shows that a multi-cylinder gasoline engine selects one of a spark ignition (SI) combustion mode or a compression ignition (CI) combustion mode, depending on the engine operating range. In the SI combustion mode, an air-fuel mixture in each of cylinders is combusted by spark ignition. In the CI combustion mode, an air-fuel mixture is combusted by autoignition. While the engine is in a predetermined low-load operating range, the engine operates in the relatively highly thermal efficient and highly fuel efficient CI combustion mode. On the other hand, while the engine is in a higher-load operating range, and is operating in the CI combustion mode, combustion noise grows. Thus, the engine operates in the SI combustion mode so as to be able to reduce such combustion noise in this range.